This application describes the use of the N-terminal propiece of the lnterleukin-1 alpha precursor molecule for the specific induction of tumor cell apoptosis. No function has ever been attributed to this pro-piece fragment. We describe the mechanisms of cellular entry, nuclear targeting, inter-action with pre mRNA splicing factors, and modulation of alternative splicing of an apoptotic protein by the IL-1 alpha propiece. In addition, we demonstrate propiece interaction with important families of proteins modulating mitochondrial function. The result is tumor cell apoptosis. Importantly, normal diploid primary human cells do not undergo IL-1 alpha propiece-induced apoptosis. The IL-1 alpha propiece maybe delivered to cells either via an expression vector or as a peptide. In the latter case the propiece enters cells by a unique and non-saturable mechanism.